1. Field of the Disclosure
The present disclosure generally relates to a method and apparatus for wireless communication, and more particularly, to a method and apparatus for processing dropped packets which include compressed headers.
2. Description of the Related Art
When internet protocol (IP) technology is applied to a wireless communication protocol, excessive overhead may be generated by packet headers which causes problems such as low transmission rates and high bit error rates on the radio link. For example, in the case of IP version 6 (IPv6) voice communication packets, data packet payload occupies only 22% of the full packet, which may lead to bandwidth inefficiency and high probability of packet discarding due to packet errors. A full packet is an IPv4 or IPv6 packet having an uncompressed header.
In order to overcome these problems, header compression has been developed, with one representative header compression mechanism being robust header compression (ROHC). When data is transmitted on a wireless network, most of the header fields of the transmitted packets in the same stream have the same value. The ROHC mechanism compresses packet headers to use a packet as a reference packet, and include only the difference information between the reference packet and the other packets in the header fields, thereby reducing packet header overhead and achieving more efficient use of bandwidth.
In a mobile communication system such as 3rd generation partnership project long term evolution (3GPP LTE), ROHC may be processed by a compressor and a decompressor in a packet data convergence protocol (PDCP) layer which is one of the layers of a wireless radio communication stack. However, when a header-compressed packet is dropped or missed in the lower layer, the compressor in the PDCP layer cannot recognize the packet drop or miss immediately. Particularly, in a unidirectional (U) mode of ROHC operation, packets are transmitted in a direction from the compressor to the decompressor, and the decompressor does not transmit any feedback to the compressor. Accordingly, when packet drop has occurred, all packets are discarded or deleted until a new reference packet is received, which may lead to call drop.